Manually operable guns are known for dispensing a multi-component fluid, such as a settable urethane foam, adhesive, and the like. Separate fluid components are fed individually to the gun, passed separately through control valves, and brought into contact with each other upon reaching a mixing chamber of a nozzle from which the mixed components are discharged as foam. Examples of such guns are found in U.S. Pat. Nos. 4,311,254 and 4,399,930 issued to Gary Harding, U.S. Pat. No. 4,762,253 issued to Steven H. Palmert, and U.S. Pat. No. 5,462,204 issued to Clifford J. Finn.
In a multi-component, such as a settable urethane foam, the two fluid components are commonly referred to as the “A resin” and the “B resin”. They usually consist of polymeric isocyanate and polyol amine, respectively. The components are supplied separately in two pressurized containers that are attached by hoses to inlets to the guns. When the two fluid components, or resins, are mixed, the mixture quickly sets up to form a rigid foam product which is substantially insoluble and extremely difficult to remove from surfaces with which it comes in contact.
The components are typically dispensed through a mixing nozzle. The gun dispenses the fluid components in a predetermined mix ratio, and the mixing nozzle mixes the components to form the multi-component fluid. The mix ratio is the ratio by volume, weight, or some other physical property, that the components of the multi-component fluid are mixed. There are a variety of mixing nozzles available which are designed to completely mix the components and produce the desired multi-component fluid. The proper mix ratio of components, however, can change over time due to the pressure of the individual components or the dispensing temperature of the components, Unfortunately, the dispensing guns do not provide any means for checking to insure the components are being dispensed at the proper mix ratio. Moreover, even if a user could determine the mix ratio of the components being dispensed, if the mix ratio is incorrect, the prior art guns do not have any means for adjusting the mix ratio.